They are also going after transactions. They want to put up some severe punishments for gun traffickers, and I imagine that they would enforce registration at the point of sale. If you make your own lower you just buy an 80% finished piece of metal and do the rest yourself. The transaction isn't controlled by gun laws and you aren't required to report anything to the government because you made the weapon yourself.

Ah, got'cha.
Never really looked into machining my own parts.
I'm more waiting for a sane administration to take over and for gun prices to come back down to earth. I may be in for a long wait.